Fix link to Hacking on Gitea on From-Source doc page (#6471)

* fix rel-ref

* fixup

docs/content/doc/installation/from-source.en-us.md

@@ -29,7 +29,7 @@ executable path, you will have to manage this yourself.
 
 **Note 2**: Go version 1.9 or higher is required. However, it is recommended to
 obtain the same version as our continuous integration, see the advice given in
-<a href='{{ relref "docs/advanced/hacking-on-gitea.en-us.md" }}'>Hacking on
+<a href='{{< relref "doc/advanced/hacking-on-gitea.en-us.md" >}}'>Hacking on
 Gitea</a>
 
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